


The Age of Billions

by Raining_on_a_stars_surface_in_space



Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Angst and Fluff and Smut, But I love guilty Byakuya so I'm adding that as angst, Guilty Byakuya, I have no idea what I'm doing, M/M, Middleschool!Senku, Second Ever Fic, Senku is close to 12 or 13 here, Shota Senku, Tease Senku, TheKingdomofShipping, This is mostly going to be smut, Will add tags as I go, not entirely sure which yet, please be nice to me
Language: English
Status: Completed
Published: 2020-01-01
Updated: 2020-01-01
Packaged: 2021-02-27 15:08:02
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, Underage
Chapters: 1
Words: 3,242
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22059052
Author URL: https://archiveofourown.org/users/Raining_on_a_stars_surface_in_space/pseuds/Raining_on_a_stars_surface_in_space
Summary: This is a fic where Byakuya and Senku slowly find out they have more than familial feelings with the other. Through a lot of smut and miscommunication, they will have a happy ending.Edit:on indefinite hiatus. Sorry. ;^;
Relationships: Ishigami Byakuya/Ishigami Senkuu
Comments: 2
Kudos: 43





	The Age of Billions

Byakuya and Senku had a relationship that was difficult to explain. Neither were blood related but they loved each other unconditionally. Ever since Byakuya adopted Senku they had an unbreakable bond. One that sometimes surpassed that of father and son. 

Byakuya always tried to be there for Senku whenever he needed him. In any way he could. Even the topics most parents don't think is good for them to engage in with their children. Like he would be more than happy to help the boy with any science project or question he may have that day. Or any of the times Senku wanted to know more about the people around him and the social structures of the world. He is always delighted to share any time he has with Senku.

They do nearly everything they can together. Byakuya invites him to help with his training to become an astronaut, and his work as a college professor. In exchange Senku invites him to help with his projects and watch movies together. It was a good system they had. It help Senku gather all the information he wanted to and it gave Byakuya an excuse to wind down when he needed a break. Neither thought it could get much better. They would have been correct in thinking that until a new situation arose and changed everything about their lives.

What changed was that Senku, small child that he was, heard from a classmate that parents and children should be physically closer together to show affection and reduce stress. Since Byakuya had a stressful job Senku thought this would be a good way to help his father feel better. This normally would not have been a problem, if it weren't for the fact that Senku decides the best way to achieve this goal and still be able to use his hands for any task in front of him, was to sit in Byakuya's lap. 

Still doesn't sound like a problem, but Senku moves around a lot while on his lap. That has effects. Effects that the older man does not want Senku to know about just yet. After all he just started puberty only a few months ago. He would be confused and maybe scared off of doing more intimate things with the person he loves some day. Byakuya does not want that to happen so he found a way for Senku to get the physical affection he wants while Byakuya won't have to worry about scaring Senku at such a young and vulnerable age.He would just leave the room if it became too much for him to hide.

His problem solving was quite effective. No other problems seemed to have come up outside of that singular one, where he sometimes had to have a quickie a door away from his son, but nothing else was wrong in the world. Until Senku asks Byakuya something he could not answer. 

"Hey dad? Why do you always leave the room not too long after I move from your lap? Do you not like me sitting here, because I can move if that's the case?"

Senku looked away dejectedly. Looking as if he already accepted that to be truth of the matter.

He starts to move as if he were getting up before Byakuya even had a chance to answer him.

"Whoa! I never said that! I like our time together Senku. It's fine if you want to continue sitting on my lap. I just have…"

He pauses trying to think of a good word to use that wouldn't tip Senku off on his particular issue.

"An adult thing to deal with sometimes. Nothing you need to worry about."

With that it seems to have relaxed Senku. He settles back into his now favorite seat, Byakuya's lap, to continue working on his homework. Though the topic seems to have been dropped for now, it was only a matter of time before Senku finds the answer he was looking for. 

'Adult thing? He has never had a problem involving me in his "adult" subjects before. So what could he be trying to hide that he doesn't want me to know about? I'll just have to find out without his help if he doesn't want to answer me.' With that thought Senku now has a determined course of action he wants to take. He just needs a plan to put into action.

_________________________________

  
  


Senku knew exactly what he wanted to do to get Byakuya out of the room so that he could follow and see just what he was doing. He just needed to get Byakuya to sit down and let him on his lap. Which would have been easy in any other situation, but today Byakuya has decided, since he has a day off, that he was going to clean what seemed like the whole apartment. 

It goes against Senku's entire plan! Which was incredibly frustrating. No matter what excuse he used Byakuya was determined to get that stain off of the stove. He had already asked for help on his research, since he had finished is homework earlier, and was told words of encouragement. That helped him feel better about his abilities, but it was not what he wanted. He tried to say he wanted to watch a movie with Byakuya and was told to either watch it himself or that he would have to wait a while. He even tried getting dirty to get Byakuya to clean him if he was so determined to clean that day, but he was disapprovingly told to take a bath and get clean clothes on.

He was running out of ideas to manipulate Byakuya to fall into his plan. He didn't know what else to do and he was running out of time to do anything. It was almost dinner time. Once bedtime came around he wouldn't be able to get to sit in Byakuya's lap until another day. He frowned down at the table he was sat at lost in thought. He didn't even notice that Byakuya won his fight to finally get that pesky stain and had asked him what he wanted for dinner.

Byakuya waited a few moments for Senku to reply, but when he didn't get one he got a bit confused. Senku doesn't usually ignore him if it doesn't involve him being incredibly interested in a problem set in front of him. However Byakuya did not see anything in front of Senku and he couldn't think of anything that might be troubling him. Instead of dwelling on it though he repeated his question in hopes that Senku just didn't hear him the first time.

Senku startled a little at hearing his dad. Realizing he was staring off into space and not getting any progress on his current dilemma he straightened and answered Byakuya. 

"Ramen. I want ramen."

"Alright. Ramen it is then! Do you want to help me Senku?" Byakuya replied enthusiastically.

"Sure." 

"Then can you get the ingredients? I'll get everything else."

Senku nods and does what Byakuya asks. He goes to the refrigerator and picks up the ingredients for the ramen they would have tonight. It was nice to get his mind off of his plan and just have a fun time with Byakuya. They threw a few of the vegetables at each other, but it worked out nonetheless. And they got some barely edible ramen out of it too.

They had just started eating when Senku realized that Byakuya was sat down right now! This might just be the best chance he'll get for the rest of the night. Knowing that Senku eats as fast as he can without getting sick. He only got a little more than half done when he notices Byakuya was almost done. But Senku was determined. He finished his bite and stood up, surprising Byakuya. 

"Huh? Hey Senku, is something wrong? You're not done with your food." 

Senku ignores the question and walks up to Byakuya and stubbornly climbs onto his lap. Not to say Byakuya was confused by the sudden behavior, but he most certainly was. Then the thought hits him. Maybe the reason why Senku was being so demanding and spacey today was because he wanted to cuddle with his dad. His dad that was busy cleaning the entire day away. That just makes Byakuya feel bad. So as compensation for not giving Senku what he obviously wanted all day, he sits still and let's Senku have his time.

Senku on the other hand was happy that Byakuya wasn't questioning why he was suddenly initiating this. Now he just needed to move around and make it seem like he was getting comfortable or was restless. Then, according to his calculations, Byakuya was going to leave the room after a few minutes. He really didn't need to pretend to be restless because he was excited to see just what Byakuya was hiding. He just couldn't stop moving around when he thought about it. 

Byakuya's breath hitched and he breathed out, "Senku…"

Then sharply stopped himself from saying something that he really shouldn't. He looked away from the squirming child on his lap with a small blush at the tips of his ears.

Senku had heard Byakuya and stilled himself waiting for him to continue. When he didn't he looked back to Byakuya and was surprised to see a blush on his face. Curious as he was Senku tried to turn all the way around to face Byakuya but paused when he felt something hard touch his thigh. 

Byakuya startled when he felt Senku touch him. He quickly moved the boy away from him and stood up. The excuse on his lips was that he needed to use the bathroom. He nearly ran for the door trying to get away from Senku as quickly as he could. 

This was it! Senku had managed to do exactly as he wanted. Now to just follow quietly and watch from a distance. Then he would know what was going on with Byakuya. The door closed loudly behind the older man. Senku snuck up to it and put his ear to the crack between the door and the wall to get the most amount of sound he could. Senku could hear a zipper and then some slippery sounds. Some moans and groans slipped out of the bathroom too.

'What's going on? Why is he making weird sounds?' 

As far as he knew those sounds don't come from going to the bathroom. So that means that Byakuya was doing something in there. Another wave of frustration zipped through Senku when he remembered that he could not watch this through the door. 

'Unless…' The young boy gripped the door knob and, as quietly as he could, turned it. There was no resistance. That means that Byakuya did not lock the door on his way in. Senku felt giddy when he cracked open the door as little as possible as to not inform the older man that he had an audience.

The sight that greets Senku is one he will never forget. At the time it was because of overwhelming confusion, but later it would be because it ended up being one of his fondest memories. The start of one of the best decisions of his life. What he saw was what looked like his father moving his hand up and down on his crotch. His crotch that was very much uncovered right now, and standing up straight in the air? 

'How does that happen?' Senku thought to himself. While he wanted to ponder more on that he knew he needed to keep his focus to observe more of this scene. Byakuya was hiding his face in his other hand trying to keep his noises down. While the hand gripping himself kept moving sometimes his thumb would touch the tip and some white liquid would gather on his hand. It seemed this liquid was making his movements easier. Which in turn made Byakuya breathe heavier and try and quiet his noises more by pressing his hand down on his mouth. It was an entrancing sight to behold. Senku didn't know any of what was happening but he was feeling warm and his breathing was also starting to get heavier whenever a louder noise was made. He couldn't tear his eyes away. 

Byakuya on the other hand was not faring well. No matter what he tried to fantasize about his thoughts kept returning to the young boy on the other side of the door. It was tearing him in two. One side thought that him masturbating while thinking of his son was hot as hell. The other side of him though, was disgusted and ashamed he would even think of Senku in such a position. 

He tried not to let it get to him. He just wanted to finish quickly so he could rejoin his boy. The older man groaned into his hand. Unable to stay completely quiet. The combination of guilt and horniness was getting to him. He started to get lightheaded. He gripped himself tighter feeling his end coming close. There was so much stimulation. From his hand working his cock, to not getting enough air from in between the fingers around his mouth, to his own head keeping his thoughts swarming, never settling on a singular one. It didn't take long before he was pushed over the edge, moaning into his hand. 

Senku gasped with wide eyes as he watched his dad's crotch spray that strange white liquid onto the floor. He watched his dad catch his breath and fix his pants. Only when Byakuya got a towel and started to clean up his mess did Senku realize he was going to get caught if he didn't move. So with quiet movements he went back to his seat. He saw that he still had some ramen left in his bowl but he didn't feel hungry after what he had just witnessed. 

He decided he would just go to bed. He was just finishing rinsing out his bowl when Byakua entered the room with a flustered look. A look that Senku only just now realized he has seen several times. He just didn't notice how it only appeared after Byakuya finished with his 'adult situation'. Senku quickly put his now rinsed bowl onto the drying rack and ran to his room. He didn't let Byakuya say anything to him. Not when he was so confused. 

Byakuya watched Senku run away from him as soon as he saw him. It broke his heart to think that the reason why might be because Senku felt neglected for being moved away when all he wanted cuddles and affection. Byakuya cursed himself for not being able to give those cuddles and affections without getting some sick and twisted feelings out of it. He didn't want to get hard when Senku sat on his lap. It was a disgusting thing to do. Especially towards his own son. Byakuya felt anger towards himself. He welcomed the ugly emotion in, hoping that it would encourage the part of his heart that loved his son in less than familial ways to go away. 

Senku though, did not share those thoughts with his father. Instead the young boy was more curious as to why and how, when he looked down, he saw his own crotch standing up. It confused him a lot because this had never happened to that part of his body before. 

Then a thought hits him, 'If my crotch goes up when I see Byakuya's crotch go up does that mean watching him do that is like a "turn on" button to my crotch?' It shocks Senku to think that, but since he doesn't know any better, he doesn't question it. 

'If my crotch acts similar to Byakuya's then does that mean I should do the same thing he did?' Senku's hand moves down to the front of his pants. He doesn't open them just yet. Trying to remember the scene that was in front of him, he thought about how Byakuya was reacting to the movement of his own hand. If Senku did the same thing would he make noises too? The only way was to experiment, but for some reason he knew he shouldn't let Byakuya find out. Not yet at least.

Senku made sure that he locked his door. He didn't want Byakuya to have the ability to see him like he had just seen Byakuya. He walked over to his desk. If he was going to do this as an experiment he should at least try this out near the place that he can document anything he needs to. 

He sat in the chair and looked back down at his groin. He unzipped himself and pulled his pants down his thighs. He had never seen his crotch stand up like this. He figured since Byakuya touched his crotch that was what Senku was supposed to do too. He hesitantly wrapped his hand around the hard rod. He gasped at the new strange sensation. That was not what he was expecting. 

Feeling excited about the possibility of new information, Senku quickly puts a hand over his mouth and starts to move the other one up and down his crotch. Just like he saw his dad do not so long ago. The sensations and feelings he was getting was mind blowing. It felt so good, and not nearly what he was expecting at all. He could see why Byakuya was having trouble staying quiet now. Senku was also struggling to keep his noises down, but the passing thought of his dad hearing him was sending him even more pleasure. 

Senku squeezes and pulls at his privates feeling something was going to happen soon. He doesn't know what it could possibly be, but his idea was that it was probably the same, strange white liquid that Byakuya's crotch ejected after a while. After all, he could see a clear like liquid beading out of the top of his crotch. He remembers that Byakuya used it as a way to make his hand move better. So Senku wiped his thumb over it and used the bit of liquid that's now on his hand to move quicker. 

The added stimulation was all Senku needed for him to release. The loud moan that passed his lips definitely should have been heard outside his door. But he couldn't think of that right now. He couldn't think of anything but the pleasure coursing through him. Once Senku calms down from the immense feeling, he pants heavily as he looks down at his hand and now soft member. The white liquid was on his hand and partly on his shirt. Just like he predicted. This was getting very interesting. 

After cleaning up as best as he can, and tucking himself away, he makes one final decision this night. He was absolutely going to need to study this and maybe, after he knows a bit more about this phenomenon, he can ask Byakuya about it again. Senku nods his head to himself with a large yawn. That is definitely what he will do. After he wakes up tomorrow. Right now he needs sleep after all that excitement and learning. The child curls up in his blankets and closes his eyes. The next day was going to be an eventful one indeed. He'll need his rest. 


End file.
